A carrier aggregation (CA) technology is mainly to aggregate multiple component carriers (CC) into one carrier with higher bandwidth, so as to support high-speed data transmission. In current Long Term Evolution (LTE) carrier aggregation, a maximum of eight carriers can be aggregated. To enable UE to aggregate component carriers on different base stations (for example, a macro base station and a micro base station), to further obtain a higher data transmission rate, a dual connectivity (DC) technology can be introduced. A main idea of the DC technology is to aggregate carriers on different base stations connected by a non-ideal backhaul link (backhaul). In dual connectivity, two cell groups or component carrier groups (CC group) are configured for one user equipment (UE). One group is a master cell group (MCG), and the other group is a secondary cell group (SCG). Specific concepts are described as follows:
A master cell group is a cell group that is associated with a master base station (MeNB) and includes a primary cell (PCell) and zero or at least one secondary cell (SCell).
A secondary cell group is a cell group that is associated with a secondary base station (SeNB) and includes a primary secondary cell (PSCell) and zero or at least one secondary cell.
A primary cell is a cell that establishes a Radio Resource Control (RRC) connection to UE. The primary cell is responsible for providing a security-related parameter, and a physical uplink control channel (PUCCH) resource is configured for the primary cell.
A primary secondary cell is a secondary cell that is included in a secondary cell group and for which a PUCCH resource is configured.
A PUCCH is mainly used to transmit hybrid automatic repeat request-acknowledgement (HARQ-ACK) information, channel state information (CSI), a scheduling request (SR), and the like.
Except for the foregoing PCell and PSCell, no PUCCH resource is configured for other cells (that is, SCells) included in an MCG and an SCG.
FIG. 1 shows an example of a typical DC scenario. UE establishes a connection to both an MeNB and an SeNB, and the MeNB communicates with the SeNB by using an X2 interface. An MCG includes cells associated with the MeNB: a PCell, an SCell 1, and an SCell 2. An SCG includes cells associated with the SeNB: a PSCell and an SCell 3. The MCG and the SCG respectively correspond to different intermediate keys (Secondary key) and layer 2 functional entities, and PUCCH resources are respectively configured for the PCell and the PSCell. In addition, when the UE performs data transmission to the MeNB or the SeNB, the UE may establish a bearer to the MeNB or the SeNB and encrypt, by using a security configuration parameter (for example, an intermediate key) of a cell group corresponding to the bearer, data transmitted over the bearer. Alternatively, the UE may establish a split (split) bearer to the MeNB and the SeNB. In this case, a part of a data packet is transmitted by using the MCG, and the other part is transmitted by using the SCG; and data transmitted by the MCG and data transmitted by the SCG are both encrypted by using a security configuration parameter corresponding to the MCG.
To further improve a data transmission rate, a massive carrier aggregation technology is introduced, to implement carrier aggregation of more component carriers, for example, carrier aggregation of 32 component carriers. However, according to an existing DC technology, if a large quantity of component carriers are introduced, an independent PUCCH, layer 2 functional entity, and intermediate key need to be configured for each SCG, and a quantity of parameters that UE needs to maintain abruptly increases. As a result, complexity of a function of the UE is increased.